Many industrial applications, especially in high stress environments require instrumentation on moving or rotating parts. In gas turbine engines it is desirable to instrument rotating turbine blades with sensors to determine b lade parameters such as strain and temperature. Signal coupling to and power for sensors on the rotating turbine blades and circuitry in the stationary mainframe has in the past been accomplished through the use of complementary inductive coils to the respective rotating and stationary engine components. Power for the sensors can be provided by a carrier signal operating at, for example 160 kHtz, that is output from a coil on the stationary member to be received by an inductive component for powering the sensors located on the rotating member. A transmitting device is located on the rotating member for broadcasting the sensor information back to a receiver o the control unit.
As the sensors and gauges typically have several functions, it is also necessary to accomplish remote wireless transmitter function switching by sending control signals to the sensors not only to instruct the sensors to switch from between operational, standby and calibration modes, but also to select which of the sensors are to respond to the command signal. Existing systems used circuitry that requires a form of permanent memory (e.g. ROM) to be placed in the electronic circuitry. The memory is then accessed by a computer matrix addressing and reading system. This function is typically accomplished through the use of known pulse generators which are large, expensive and are limited in terms of total pulse width and the number of pulses which can be transmitted.
It would be advantageous to have a telemetry pulse encoding system for use with a sensor control system which is inexpensive and simple in construction. The present invention is directed towards such a system.